Prosthetic heart valves are now widely used to replace natural diseased valves of the human heart. Prosthetic heart valves are either of the mechanical or leaflet type.
A leaflet-type prosthetic heart valve typically includes a frame or stent, valve leaflets coupled to the frame and a sewing ring to enable the valve to be sutured into the heart at an appropriate location. The frames are typically constructed of wire as shown, for example, in Carpentier et al U.S. Pat. No. 4,106,129 or of sheet material as shown, for example, by Ionescu et al U.S. Pat. No. 4,084,268. In either event, the properties of the base and commissure supports are derived from the same construction, i.e., a wire or sheet material. Unfortunately, it is sometimes desirable that the commissure supports and the base have different properties or characteristics. Thus, the selection of the particular wire or sheet material of necessity represents a compromise between the desired properties of the commissure supports and the base.
For example, an all-wire frame may have a base which is too deformable. Conversely, a sheet material frame may provide commissure supports which are too rigid and tend to cause tearing of the valve leaflets.
In addition, to make a wire frame, opposite ends of an elongated wire must be joined together to form an annular frame. The splicing together of the opposite ends of the wire forms a discontinuity in the frame which can be troublesome.
In a leaflet-type prosthetic heart valve, it is necessary that the valve leaflets extend over an outflow edge or distal edge of the frame. When implanted, the valve leaflets repeatedly open and close, and this causes some abrasion of the valve leaflets by the distal edge. It is known to pad the distal edge of the frame as shown, for example, in Ionescu et al U.S. Pat. No. 4,084,268 and in European Patent Application No. 0150608. However, prior art padding techniques have not been as sufficient as desired in reducing abrasion of the valve leaflets because the pad is believed to lose its cushioning ability after long periods of use.